Teofilin Baskılı Kriyojellerin Sentezi ve Karakterizasyonu
Özet
In this thesis, it is aimed to develop an effective adsorbent for theophylline removal from water by synthesis and characterization of theophylline-imprinted poly(2-hydroxyethyl methacrylate/acrylamide) cryogel membranes in tablet form. Cryogel membranes in tablet form were synthesized by chemical method at very low temperatures. The advantages of theophylline suppression and acrylamide over 2-hydroxyethyl methacrylate are discussed. It has been observed that the presence of acrylamide in cryogel membranes and theophylline suppression increase the adsorption capacity. The synthesized cryogel membranes were characterized for structural, thermal and porosity by Fourier Transform Infrared Spectroscopy, Thermogravimetry, Scanning Electron Microscopy, and Branuer Emmett and Teller surface porosity analysis. It has been observed that the total surface area and pore volume for imprinted cryogel membranes have a higher value than non-imprinted cryogel membranes. Data from percent swelling tests at equilibrium showed that the structure had a certain macroporosity. Macroporosity was observed as 55.2% in theophylline released poly(2-hydroxyethyl methacrylate/acrylamide) cryogel membranes. According to the average data obtained from the Branuer Emmett and Teller surface porosity results, the presence of micro and mesopores other than macropores in poly(2-hydroxyethyl methacrylate/acrylamide) cryogels was evaluated. The theophylline amount was determined by Ultraviole and visible light absorption spectroscopy and the maximum value of the adsorption capacity of theophylline-imprinted and non-imprinted cryogel membranes was found to be highets at pH 7, and this pH value was used for all studies. The maximum adsorption capacity for imprinted cryogels was determined as 16,2 mg/g at pH 7. It was observed that the adsorption capacity of 2-hydroxyethyl methacrylate cryogel membranes that do not contain acrylamide was not affected by pH value. The effect of ionic strength on adsorption capacity was tested by using sodium chloride and sudium sulphate. It was determined that the ionic strength decreased the adsorption capacity, and it was concluded that theophylline diffused into the structure by making hydrogen bonds. While it was observed that 0.5 M sodium chloride reduced the adsorption capacity to 14 mg/g, this value was observed as 13.1 mg/g for sodium sulfate at the same concentration. It has been observed that the adsorption capacity of the cryogel membranes varies inversely with the mass of the cryogel membranes in the solution containing constant theophylline concentration, while the adsorption capacity is 36.3 mg/g for 0.018 grams of cryogel, this value is observed as 16.2 mg/g for 0.12 grams of cryogel. In the theophylline solution interacting with the constant mass cryogel membranes, it was observed that the adsorption capacity changed directly with the theophylline concentration, and the adsorption capacity was observed as 16.2 mg/g for 0.12 grams of cryogel in a solution containing 400 ppm theophylline. In the theophylline solution interacting with the constant mass cryogel membranes, it was observed that the adsorption capacity changed directly with the theophylline concentration, and the adsorption capacity was observed as 16.2 mg/g for 0.12 grams of cryogel in a solution containing 400 ppm theophylline. No change in adsorption capacity was observed at higher theophylline concentrations. Adsorption capacities were measured at temperatures ranging from 15°C to 60°C and it was observed that they changed inversely with temperature. According to the change of standard enthalpy change values, the adsorption process is exothermic, and according to the change of standard Gibbs free energy change and standard entropy values, the adsorption of theophylline on 2-hydroxyethyl methacrylate/acrylamide cryogel membranes is involuntary. Depending on the temperature, the standard Gibbs energy change value was found to be (9,053-7,126) kJ/mol, the standard enthalpy change value was -6.2 kJ/mol and the standard entropy change value was -46.0 kJ/mol. The adsorption isotherm modeling was performed for Langmuir and Freundlich isotherms, and it was determined that the adsorption process was more suitable for the Langmuir isotherm. According to this modeling, the maximum adsorption capacity was 30.3 mg/g, the separation factor was between 0 and 1 at all concentrations, and the Langmuir constant was 4.49 x 10-3 L/mg. The interaction time of theophylline with 2-hydroxyethyl methacrylate/acrylamide cryogel membranes was followed and it was observed that adsorption equilibrium was reached in 30 minutes. Pseudo-first-order and pseudo-second-order kinetic models have been tested for adsorption processes and it has been observed that the adsorption process fits the pseudo-second-order modeling. In this modeling, the theoretical adsorption capacity was found to be 13 mg/g and the adsorption rate constant was found to be 0.1mg/(L.min). The maximum desorption capacity of theophylline from cryogel membranes was found to be 15.2 mg/g (%94) at pH 3. It has been determined that poly(2-hydroxyethyl methacrylate/acrylamide) cryogel membranes can be used 10 times while maintaining their chemical and physical stability.
